There has been known an EGR (Exhaust Gas Recirculation) system that returns a part of exhaust gas flowing in an exhaust passage to a combustion chamber through an intake passage, and then, decreases the combustion temperature of an air-fuel mixture staying inside of the combustion chamber, so as to reduce the ratio of nitrogen oxide to the exhaust gas. In this EGR system, an EGR control valve capable of opening or closing an EGR passage is interposed in the EGR passage communicating with the intake passage and the exhaust passage at both ends thereof, thereby recirculating the exhaust gas toward the intake passage in a predetermined operational region.
In recent years, a social demand for purification of exhaust gas has been remarkably escalating. From this point of view, the operation of an internal combustion engine is stopped during the halt of a vehicle, thus suppressing waste consumption of fuel, and further, preventing waste emission of carbon dioxide at the same time, that is, promoting an idle stopping control. However, there is no effective exhaust gas at the EGR passage when the internal combustion engine is started again during the idle stopping control, and therefore, it is difficult to contain the exhaust gas in the intake air that is supplied to the combustion chamber together with the fuel at the beginning of the start.
Patent Literature 1 has proposed a technique for solving the above-described problem. Specifically, EGR gas is temporarily reserved in an EGR passage at the time of the stoppage of an internal combustion engine during idle stopping control, and then, the EGR gas can be supplied to one cylinder that initially burns fuel to be first supplied, in particular, has been burnt as well as the intake air when the internal combustion engine is started again.